What is the ACL?

The ACL is a very strong ligament on the inside of the knee. It runs from the femur (thigh bone) obliquely down to the Tibia (shin bone). The ACL prevents the tibia (shin bone) from moving forward relative to the femur (thigh bone). The ACL is very important in stabilising the femur and tibia and prevents the knee from “giving way”.

This is especially important for knee actions such as side-stepping in sport, pivoting and jumping. If the ACL is injured and the knee gives way (unstable knee) then other structures in the knee will also be injured such as bone, cartilage and meniscus injuries.

How is the ACL injured?

The ACL is most commonly injured during sport with pivoting, twisting or side-stepping actions. The ACL can also be injured with a direct blow to the knee or with extreme flexion (bending) or extension (straightening) of the knee.

What happens to the knee when the ACL is ruptured?

A popping or snapping sound may be heard, followed by intense knee pain and swelling. It will be too painful to bear weight on the affected lower limb. The swelling and pain may settle after a few days to weeks, but as soon as pivoting or side-stepping is done you may feel that the knee is unstable resulting in pain and swelling again.

What happens to the knee when the ACL is ruptured?

How is an ACL injury diagnosed?

Xray: An Xray of the knee is always the first investigation to be done. Fractures, cartilage damage and knee fluid may be seen on X-rays. X-rays may also show subtle features of an ACL disruption (e.g. Second fracture)

MRI: A MRI of the knee is the gold standard investigation to diagnose an ACL injury. Ligament, meniscus, cartilage and bone injuries can also be seen on an MRI. This is important as an ACL injury rarely occurs in isolation.

Knee Arthroscopy: ACL injuries can be diagnosed with a knee arthroscopy (camera in the knee), this is usually done if an MRI is not available.

Can an ACL injury be treated non-surgically?

Not everyone needs an intact ACL. Most older sedentary individuals who do not engage in sport may be perfectly happy without an ACL ligament. If however you are young and engaged in a sport requiring jumping, pivoting and sidestepping you will need an ACL reconstruction.

An ACL deficient knee is an unstable knee resulting in the knee “giving way”. These “giving way” episodes causes internal knee damage and may result in early-onset osteoarthritis of the knee, this, in turn, may result in a knee replacement at a young age.

What is the surgical treatment of an ACL deficient knee?

The ACL ligament is one of the strongest ligaments in the body and is responsible for resisting great forces in the knee during pivoting, side-stepping and jumping. An ACL injury will not heal on its own and a torn ACL ligament cannot simply be sutured. The torn ACL ligament is removed and a new ligament (usually taken elsewhere in the body) is used to make a new ACL ligament. This is done arthroscopically (through small portholes in the knee using a camera).

The new ligament (known as a graft) can either be an autograft (using your own tissue) or allograft (tissue from a cadaver).

The Autografts (most commonly used) options are:

1. Hamstrings (Gracilis and Semitendinosus)
Your hamstrings are harvested from a small incision on the inside of the knee. This is an excellent graft and not shown to cause weakness of the hamstrings

2. Bone-patella-Bone
The middle third of your patella tendon is harvested along with a small piece of bone from your kneecap (patella) and shin bone (tibia). This is also an excellent graft but may lead to kneecap pain and in rare cases kneecap fractures.

3. Quadriceps
A small strip of your quadriceps tendon is harvested and use to reconstruct the ACL ligament. This is also an excellent graft


These grafts are also excellent. Because the tissue is not taken from your body the surgical time is shorter. These tissues are screened for infections such as Hepatitis and HIV. The risks of contracting infections from allografts are extremely low.

What are the complications of Surgery?

Complications specific to ACL surgery include knee stiffness, prolonged knee pain, continued ACL instability and rupture of the new ACL ligament.

Complications common to all surgery include infections, bleeding, nerve damage, blood clots (DVT) or problems with anaesthesia.

What happens after surgery?

After surgery, the physiotherapist will see you and discuss the postoperative rehabilitation programme. You will be provided with crutches and a knee brace. You will have a bulky dressing on your knee. Usually, patients are able to go home the same day or the next day if the pain is not controlled.

After discharge, we will contact you with a date to see the wound sister for a wound check 2 weeks after surgery. Immediately after seeing the wound sister you will see the physiotherapist (Barnard and Van Wyk Physios). These appointments will be arranged for you by our Receptionist. It is important that the dressings are kept clean and dry until you see the wound sister at your 2-week appointment. If you have any concerns regarding your wounds (swelling, redness, pain, oozing or pus) please contact the rooms.

The physiotherapists will arrange follow up appointments with you.

You will see me (Dr Solomon) 6 weeks after surgery to evaluate your progress. If there are any concerns before then you must contact my rooms.

Your discharge medication will include pain relief medication and blood thinners to prevent blood clots.

You are encouraged to place ice over your wounds for 30 mins every hour as often as you can for the first 2 weeks.

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